Putative relationships among inseminating and externally fertilizing characids, with a description of a new genus and species of Brazilian inseminating fish bearing an anal-fin gland in males (Characiformes: Characidae)

Hans-georg Evers; John R. Burns; Naércio A. Menezes; Stanley H. Weitzman

摘要

A new inseminating fish species of the family Characidae, Bryconadenos tanaothoros, from tributaries of the upper rio Xingu and upper rio Tapajós basins, Mato Grosso, Brazil is described as the type species of a new genus. This new species and the genus are characterized by a glandular organ on the anterior region of the anal fin of sexually mature males, curved lower jaw teeth, and an inseminating reproductive mode. This new genus is hypothesized as most closely related to Attonitus, a genus with three inseminating species from Peru. Bryconadenos and Attonitus are suggested as related to certain inseminating, but undescribed characid species of uncertain relationships that are similar in certain respects to species of the glandulocaudine Planaltina and to the inseminating species of Knodus. These and a few other inseminating characids are included in a previous tentative characid subgroup designated as Clade A. No species among a relatively small sample of the many species of the Clade A genus Bryconamericus were found inseminating, except Bryconamericus pectinatus. However, newly collected specimens of B. pectinatus were found to have caudal-fin squamation like that of the species of Knodus and this species is here tentatively referred to Knodus. Our investigations indicate that at least several species of Knodus, including the type species, Knodus meridae, are not inseminating, but we found two inseminating apparently new characid species that currently would be referred to Knodus. These species lack the derived anal-fin rays present in the males of K. pectinatus. Other Clade A taxa known to be inseminating, such as two species of the large genus Creagrutus, three species of Monotocheirodon (two undescribed), and the species and genera of the characid subfamily Glandulocaudinae are briefly discussed regarding possible relationships to Attonitus and Bryconadenos. The anatomical aspects of the primary and secondary sexual characteristics of Bryconadenos and Attonitus are discussed in relation to certain other inseminating characids, such as the species of Brittanichthys and Hollandichthys, that are not currently hypothesized to belong to Clade A and presumably acquired insemination independently. It is concluded that much additional data regarding the reproductive modes as well as other anatomical/physiological systems of characids currently included in and excluded from Clade A are necessary before a reasonably supported phylogeny of Clade A characids and their possible outgroup relatives can be advanced. The anal-fin gland cells of sexually active male Bryconadenos specimens are histologically indistinguishable from club cells (also called alarm substance cells) found within the skin of cypriniforms, characiforms, catfishes, and other otophysan fishes. These cells occur at the skin's surface of the anal-fin gland in male Bryconadenos where they are organized into an organ. Many other adult male characids have club cells at the anal-fin's skin surface, often associated with anal-fin hooks, but were not found organized into an organ as in Bryconadenos. We hypothesize these cells to secrete a pheromone during courtship via holocrine secretion. Males of the genera Lophiobrycon , Glandulocauda, and Mimagoniates, tribe Glandulocaudini, were found to have club cells associated with their caudal-fin organ, but no specialized mucus cells were present as found in the caudal organ of males of the glandulocaudine Corynopoma riisei, tribe Stevardiini (= Corynopomini of past authors). In this species, males have hypertrophied mucus cells hypothesized to be modified for pheromone secretion. Evidence that the derived scales and fin rays of the caudal organ of males of the tribe Glandulocaudini are not homologous with that of other tribes of the Glandulocaudinae, as this subfamily was previously recognized, is discussed and it is concluded that the members of the tribe Glandulocaudini should be recognized as a separate subfamily, the Glandulocaudinae, with possible close relationships to some other Clade A inseminating characids that lack caudal-fin organs. The remaining tribes of the former Glandulocaudinae are here included in the subfamily name Stevardiinae. Many species of these two subfamilies and some of the other inseminating Clade A characids have modified sperm cells with an elongate "binding"cytoplasmic collar and mitochondria located along and beyond the nucleus. This may be an indication of a relationship at a unique level within Clade A characids. However, further research on the derived nature and homology of the sperm cells within inseminating Clade A characids and of the caudal organs of the tribes of the Stevardiinae must be undertaken in order to utilize sperm cell features as characters for studying phylogeny. Finally, the kinds of secretory cells and gross anatomical structures in the tail organs of the stevardiine tribes need detailed research in order to better present hypotheses of phylogeny for t

机译：来自巴西马托格罗索州上里约新古河和上里约Tapajós盆地支流的查拉迪科家族的一种新的授精鱼类，Bryconadenos tanaothoros，被描述为一种新的鱼类。这个新物种和属的特征是性成熟男性的肛门鳍前部的腺体器官，弯曲的下颌牙齿和授精的生殖方式。据推测，该新属与来自秘鲁的三个授精种的阿托尼托斯属（Attonitus）关系最密切。 Bryconadenos和Attonitus被认为与某些授精有关，但未描述的不确定酸的特征性物种在某些方面与腺乳头Planaltina和Knodus的授精物种相似。这些和其他一些人工授精的酸包括在先前的暂定性的酸性亚基中，称为进化枝A。在进化枝A属Bryconamericus的许多物种中，只有一个相对较小的样本中没有发现任何物种，除了Bryconamericus pectinatus。然而，发现新收集的果蝇B. pectinatus标本具有尾鳍鳞片状，类似于克诺杜斯种，此处暂将其称为克诺杜斯。我们的研究表明，至少没有几种Knodus物种，包括典型的Knodus meridae类型，但我们发现了2种可能是新近被称为Knodus的隐性新的酸性物种。这些物种缺乏在K.pectinatus的雄性中存在的衍生的肛门鳍射线。简要讨论了其他已知的Clade A类群，例如Creagrutus的两个大种，Monotocheirodon的三个大类（两个未描述）以及Characid亚科Glandulocaudinae的大类和属，以探讨它们与Attonitus和Bryconadenos的可能关系。结合其他某些授精性炭酸（例如不列颠嘴and属和荷兰Holland嘴属的物种），讨论了Bryconadenos和Attonitus的主要和次要性特征的解剖学方面，目前尚不认为它们属于进化枝A，并且大概是独立获得的。结论是，在合理地支持进化枝A的酸性物质及其可能的亲缘亲缘关系的系统发育之前，有关目前包括在进化枝A和不包括在进化枝A中的酸性的生殖方式以及其他解剖/生理系统的大量其他数据是必要的。在组织学上，与具有性活动的雄性Bryconadenos标本的肛门鳍腺细胞区别于在鲤形，characiforms，cat鱼和其他otophysan鱼的皮肤中发现的俱乐部细胞（也称为警报物质细胞）。这些细胞出现在雄性Bryconadenos的肛门鳍腺的皮肤表面，在那里它们被组织成一个器官。许多其他成年男性性酸在肛门鳍的皮肤表面具有俱乐部细胞，通常与肛门鳍钩相关，但并未发现它们像在Bryconadenos中那样组织成器官。我们假设这些细胞在求偶过程中通过全分泌激素分泌信息素。 Lophiobrycon，Glandulocauda和Mimagoniates属的男性，即Glandulocaudini部落，具有与它们的尾鳍器官相关的俱乐部细胞，但是在Glandulocaudine的Corynopoma riisei部落的男性的尾aud器官中，没有发现专门的粘液细胞。 Stevardiini（=以前的作者的Corynopomini）。在这个物种中，雄性具有肥大的粘液细胞，据推测可以对其进行信息素分泌进行修饰。讨论了先前发现的Glandulocaudini部落男性尾鳍的鳞片和鳍条与其他Glandulocaudinae部落的同源的证据，并得出结论，得出结论，Glandulocaudini部落的成员应该被认为是一个单独的亚科，Glandulocaudinae，可能与缺乏尾鳍器官的其他一些Clade A授精糖酸有着密切的关系。前Glandulocaudinae的其余部落在此包含在亚科Stevardiinae中。这两个亚家族的许多物种以及其他一些人工授精的进化枝A酸已经修饰了精子细胞，这些精子细胞具有沿着细胞核及沿细胞核之外延伸的细长的“结合”胞质领和线粒体。这可能表明在Clade A酸类中具有独特水平的关系。然而，为了利用精子细胞的特征作为研究系统发育的特征，必须对精子A进化枝中的精子细胞和Stevardiinae部落的尾部器官的精子细胞的衍生性质和同源性进行进一步的研究。最后，需要进一步研究Stevardiine部落的尾部器官中分泌细胞的种类和总体解剖结构，以便更好地呈现t的系统发育假说。

Putative relationships among inseminating and externally fertilizing characids, with a description of a new genus and species of Brazilian inseminating fish bearing an anal-fin gland in males (Characiformes: Characidae)

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